To understand the biologic mechanisms responsible for osteoblastic and osteolytic malignant lesions To subclassify metastatic bone disease according to appearances on MRI/Bone Scan (BS)/CT scans and demonstrate that patterns reflect underlying biology To discuss how multiparametric imaging allow the creation of biologic models, enabling improved understanding of imaging phenotypes

At a cellular level, interactions between tumour, bone marrow mesenchymal cells (via cytokines) results in distinct imaging phenotypes, through promotion and/or inhibition of both osteoblastic and osteoclastic recruitment and activity. Bone metastasis characterisation using diffusion MRI allows categorization based on the degree of cellularity. Multiparametric imaging with CT/Fat%/BS allows metastasis appearance to be related directly to underlying biology. We describe with examples, 7 sub-categories of bone metastasis hypothesising corresponding molecular and cellular mechanisms ( Fig. 1 ) Pattern 1 - Osteolytic, predominantly fatty (osteoporotic myeloma...

Let's begin by an example case: Is this appearance unusual? Not really, it is seen quite often in day to day oncological imaging. Why? Theapperancesof bone metastases really depends on the degree of cellularity and sclerosis associated with that tumour type.Wehighlight 7 patterns of bone metastasis on imaging, their individual pattern, likely tumour phenotypes and hypothesise the potential causes for this. Is this important? Well it is if you care to consider why various bone metastases have a reduced sensitivity to detection on different imaging...

Multiparametric bone marrow imaging of metastases : Allows us to understand biologic mechanisms responsible for osteolysis/osteoblastic lesions Fig 8. Allows classification of bone metastases according to underlying cellularity & matrix status Fig. 9 Multiparametric imaging in therapy response settings can show how biologic models enable improved understanding of imaging appearances

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Dr Danoob Dalili MB BS FRCR Specialist Registrar Clinical Radiology, Imperial College London, UK Research fellow, Guy's & St Thomas' NHS Foundation Trust, London, UK Dr Andrew GogbashianMB BS MRCS FRCR Consultant Oncological Radiologist Paul Strickland Scanner Centre, Mount Vernon Cancer Centre, London Professor Anwar Padhani MB BS MRCP FRCPFRCR ConsultantRadiologist and Professor of Cancer Imaging Paul Strickland Scanner Centre, Mount Vernon Cancer Centre, London